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xi                                 ANCESTRY OF CAMELS                             289

period, and for a long time after, there were no types referable to
the Camelidae in the Old World. Though a Camel in many
features of its organisation, Poebrotheriutn was " generalised " in
many ways. Thus the metacarpals and metatarsals were not
fused to form a cannon bone, and the two lateral digits were
represented by splint rudiments of metacarpals and meta-
tarsals. The dentition was complete. The skull though
distinctly Tylopodan, also shows more generalised characters.
Thus the .orbit is not quite, though nearly, completed by bone.
In the Camel it is quite closed. The nasal bones are much
longer, reaching nearly to the end of the snout. The odontoid
process of the axis vertebra is not spout-like as in existing
forms, but cylindrical, though slightly
flattened upon the upper surface. The
scapula is described as being more like
that of the Lama than of the Camel,
though variations occur which approxi-
mate to the CameL The brain, judging
of course from casts, has those sulci
" which are common to the whole series
of Ungulates, and closely resemble those
of a foetal Sheep."                                  FlG ^sT^A^rioTTTrface of

Later in historical sequence than axis of Bed Deer. xf. 0,
Poebrotherium, and structurally inter- tericn^zygniSphySs*; S fora-
mediate between it and Protolabis,, IS        ue for second spinal nerve,
.,-,.-. ,~ -T ,7 -r*         (From "Flower's Qst eulogy.)

the Miocene genus Gomphothervu.wi.    It                                  VJ

shows an advance in structure upon PQebrotJierium, in that the
orbit is completely encircled by bone, though the posterior wall
is thin; jhe lower canines instead of being incisiforxn are curved
back as in later Camels, and separated by a wide diastema from
the preceding and the succeeding teeth.

Later in age than PoebrotJierium is Protolabis, a Tylopod in
which the full number of teeth is still retained ; its skull
presents no particular changes from the Poebrotherine type; the
nasals, however, are somewhat shortened.

Later still in point of time is P1rocamelii<8. In this form we
have apparently an ancestral stock, whence both Camels and Lamas
were derived. The upper incisors are as in existing forms, but
the first and- second persist for a somewhat longer time. The
skull shows two well-marked types of structure; in P. oecidentalis

TO!,. X                                                                                                 "O"